Techniques for performing the automated closing of tubular knitted articles, particularly hosiery items, at an axial end thereof, i.e., the toe in the case of hosiery items, at the end of their production on circular hosiery knitting machines, are known.
Some of these techniques are based on picking up the article, at the end of its production, from the circular hosiery knitting machine and on transferring it to a sewing or looping station, which is generally arranged laterally with respect to the machine used to produce the article.
In the sewing or looping station a sewing or looping head is arranged, by means of which the axial end of the article, usually constituted by the axial end at which the production of the article has ended, is closed.
Some techniques are based on the use of a single device both to pick up the article from the machine that produced it and to support the article during the sewing or looping operation to close its axial end. In other techniques, a device is provided for picking up the article and transferring it to the sewing or looping station and a handling device is provided that is arranged in the sewing or looping station and is used to prepare the article for the subsequent sewing or looping operation and optionally to move the article during sewing or looping with respect to the sewing or looping head.
Usually, the article is picked up from the machine that produced it and optionally transferred to the handling device by engaging individually the loops of knitting of the last row of knitting of the article, and the loops of knitting of a half-row of such last row of knitting are made to face individually the loops of knitting of the other half-row before proceeding with sewing or looping, so that the axial end of the article is closed by joining in each instance two mutually facing loops of the two half-rows that compose the last formed row of knitting. Thanks to this fact, an excellent result is achieved in terms of precision and aesthetics in the automated closing of axial ends of tubular knitted articles, particularly in the automated closing of the toe of hosiery items.
In other techniques for performing automated closing of the toe of hosiery items, the element that supports the article during sewing or looping is constituted by one half of the same needle cylinder of the machine used to produce the article, since at the end of the production of the knitted article one half of the last formed row of knitting is transferred, loop by loop, by means of an appropriately provided element, from the needles that produced it to the needles that have produced, and are still retaining, the loops of knitting of the other half of the same row.
Substantially, the automated closing of an axial end of a knitted article, particularly of hosiery items, is performed by supporting the article by means of a half-ring element provided with a plurality of spikes, which are uniformly spaced one another around the axis of the ring and on each of which two loops of knitting are arranged, one belonging to one half of a row of knitting and one belonging to the other half of the same row of knitting. The sewing or looping head that is used is generally provided with two elements, for example two needles or a needle and a crochet, which cooperate in order to form a sewing chain stitch. One of these two elements, which are actuated synchronously with respect to each other and with respect to the rotary motion of the half-ring about the axis of the ring, enters with its spike, in each instance, in a pair of loops of knitting that is carried by a same spike of the half-ring element so that the sewing chain stitch progressively ties together the several pairs of loops, thus closing the axial end of the knitted article.
These sewing or looping heads can generally move toward and away from the half-ring that supports the article to be sewn or looped, so that they are closer to the half-ring during the sewing or looping operation and are spaced when they are inactive, so as to avoid causing hindrance during the operation for transferring the loops of knitting onto the spikes of the half-ring and during the operation for removing the article at the end of sewing or looping. Moreover, these sewing or looping heads are equipped with a cutting element to cut the sewing chain stitch at the end of the sewing or looping operation.
The cutting elements with which these sewing or looping heads are equipped are generally arranged downstream of the region where the sewing chain stitch forms along the direction of rotation of the half-ring that supports the article during sewing or looping, and are constituted generally by a hook-shaped element that can move on command so as to engage the portion of the sewing chain stitch that extends from the last spike of the half-ring that passed in front of the pair of sewing elements, and the sewing elements themselves. A clip and a blade are respectively laterally adjacent to the hook-shaped element and are designed respectively to engage the sewing chain stitch and to cut it.
In this manner, the portion of the sewing chain stitch that is engaged with the article is separated from the sewing or looping head, while the remaining portion of the sewing chain stitch, which extends from the hook-shaped element to the sewing elements, remains clamped, with its end, between the hook-shaped element and the clip.
These sewing or looping heads suffer some drawbacks, which are mainly due to the cutting element that is used.
The arrangement of the cutting element, which is spaced downstream of the sewing elements along the direction of rotation of the half-ring that supports the article during the sewing or looping operation, forces the provision of a portion of sewing chain stitch that is in excess at the end of the sewing portion performed on the article to allow the final end of the sewn portion of the article to face the hook-shaped element so that it can engage the sewing chain stitch in order to cut it. This portion of excess sewing chain stitch is cut by the cutting element at the end of the sewing process proximate to the final end of the sewn portion of the article and, in order to prevent it from being able to remain on the article, at the beginning of a new sewing process when the initial end of the sewn portion of the article passes proximate to the hook-shaped element. In this cut, at the beginning of the new sewing operation, the cutting element is assisted by a suction port, which retains the portion of sewing chain stitch while the hook-shaped element is disengaged and again engaged with the sewing chain stitch portion proximate to the article. This excess sewing chain stitch, which is spaced from the suction port, in case of large productions, is a considerable waste of yarn and therefore constitutes an additional cost.
Moreover, this provision of an excess sewing chain stitch portion, together with the need to rotate, once the sewing operation has ended, the half-ring through an additional arc in order to move the excess sewing chain stitch into a position that is adapted for it to be engaged by the hook-shaped element, inevitably increases the time needed to complete the sewing or looping operation and consequently has a negative effect on the overall time required by the operation for automated closing of the axial end of the article. Moreover, this time increase is worsened by the fact that generally the half-ring, after the cutting element has cut the sewing chain stitch, must be returned to the initial position by means of a rotation in the opposite direction about the axis of the ring.